This invention relates to a differential apparatus for use in a vehicle.
"A differential-limiting type differential apparatus" is disclosed in Japanese Utility Model Laid-Open Publication (Kokai) No. 1-166157. This apparatus is a planetary-gear differential apparatus of double-pinion type, which is provided with a differential limiting mechanism. A drive force of an engine is inputted to an internal gear, and is divided into left- and right-hand driving axles from pinion carriers and a sun gear.
In the case of the above-described publication, however, differential limiting means includes a multiple disc clutch between a differential case and a planetary carrier. For this reason, there are problems that a structure or construction is complicated, and the apparatus is large-sized.
In order to dissolve the above-mentioned problems, applicant of the present invention has previously filed Japanese Patent Application No. 2-188136.
As shown in FIG. 1, it is assumed that, when an internal gear 201 is rotatively driven in an arrowed direction, and when a wheel on the side of a sun gear 203 is idle-run, a torque (idle-running torque) applied to the sun gear 203 is T.sub.SP, while a torque (grip torque) applied to the sun gear 203 when the wheel on the side of a pinion carrier is idle-run is T.sub.G. Then, T.sub.G remarkably increases more larger than T.sub.SP by a driving resistance inputted from the wheel on the side of the sun gear 203.
Further, a resultant force of a drive torque and a reaction force thereof acts upon each of rotating sections of pinion gears 205 and 207 and pinion carrier. A rotating resistance (differential limiting force) due to a frictional force in accordance with a magnitude of the resultant force is generated on each of the rotating sections.
Accordingly, the differential limiting force is large when the wheel on the carrier side is idle-run, while the differential limiting force is small when the wheel on the sun gear side is idle-run. Thus, an unbalance in strength of the differential limiting force occurs between the left-and right-hand wheels, so that a pull of differential limiting occurs. Furthermore, since the differential limiting force is in proportion to the frictional forces of the respective rotating sections, the pull becomes more remarkable the more the differential limiting force increases. In the case where the torque is inputted from the sun gear, such pull occurs on the side of the internal gear.
As the differential limiting force increases, a torque distribution ratio (transfer ratio) between the idle-running side at the time one of the driving wheels is idle-run and the other driving-wheel side, so that rough-road bailing-out or escaping performance is improved. If, however, the transfer ratio increases as described above, a pull of differential limiting between the left- and right-hand wheels increases so that the rough-road bailing-out performance in the case where the wheel on the side of the sun gear is idle-run decreases. Thus, an unbalance occurs in cornering characteristic between left turn and right turn. An unbalance in direct or rectilinear advance stability also occurs between the right-hand direction and the left-hand direction. Accordingly, maneuvering stability is remarkably reduced.